Thermodynamically-controlled switch



M. H. BAKER, DECD,

M. H. BAK R. ADMINISTRATRIX. THERMODYNAMICALLY CONTROLLED SWITCH.APPLICATION FILED SEPT. 17, I915. RENEWED IUNE 11, 1919.

Patented Mar. 16, 1920.

UNITED STATES PATENT curios MALCOLM I-I. BAKER, OF BRAIN TREE,MASSACHUSETTS; MARIE H. BAKER, ADMINISTRA- v TRIX OF SAID MALCOLM H.BAKER, DECEASED, ASSIGNOR TO KENNETH W. CROSBY,

TRUSTEE, or BOSTON, MASSACHUSETTS.

Specification of Letters Patent.

Patented Mar.16,1920.

-App1ication filed September 17, 1915, Serial No. 51,206. Renewed June11, 1919. Serial No. 303,476.

To all whom it may concern:

Be it known that I, MALCOLM H. BAKER, a citizen of the United States,and a resident of Braintree, in the county of Norfolk and Commonwealthof Massachusetts, have invented certain new and useful Improvements inThermodynamically-Controlled Switches, of which the following is aspecification.

My invention relates to electric switches involving in their operatingmechanisms thermo-dynamic means for partial automatic control and hasfor its object, generally, to provide in such switches an arrangement ofthe thermo-dynamic controlling means whereby designed circuit-governingaction of the switch may automatically be caused when such means. arethermally energized and particularly, but not exclusively, when suchmeans are so energized by the electric current.

More specifically, the object is to thermodynamically control therelative movement of electrical contacts in such manner that saidmovement is permitted to occur a predetermined time after designedenergization of the thermo-dynamic controlling 1neans,- or, in otherwords, to introduce a time element, comprising the operative period of athermo-dynaniic device active to free the contacts for relativemovement, between the act of energizing the said device and the actualmaking or breaking of the circuit.

As a preferred and specific embodiment of my invention, I haveillustrated it herein as a time controlled, thermostatically governed.circuit breaking device,-and the particular form of such device that Ihave chosen for illustrative purposes is a oneway snap switch, of thesingle pole type, and of a common and well known mechanical arrangement.I

My invention may. however, be equally well applied to any other form ofswitch, such as a blade knife, push button, lamp socket, pendant. cordpull. or magnetically interval, varying from some ten seconds toa fewminutes after manual extinguishment causing actuation of the switch andbefore material convenience, but often an actual safeguard againstaccidents.

That is, conditions of attainment being equally easy and reliable, alight which involved such continuation would practically always bechosen over one which did not.

My invention accomplishes this result not only in a simple and cheapmanner, but in one which is absolutely reliable and durable,commercially.

In carrying out my invention, as specifically illustrated and describedherein, I employ the usual snap switch,and I also employ a detentadapted to retain the switch contacts closed after the button has beenturned to the off position, and other detent means to hold the button atsaid off position after it has been so turned. And I provide athermo-dynamio device, adapted to be energized by the electric current,to free the said first detent means and permit the opening of the switchcontacts after a predetermined time, the said thermo-dynalnic devicebeing energized by the act of turning off the button.

For operatively energizing the thermodynamic device I may use anysuitable electrical resistive unit, but I preferably employ a winding ofresistance wire arranged in heating relation to said device.

' I have illustrated my invention in theannexed drawings, in whichFigure 1 is a plan view, with the casing and control button removed andthe parts shown in the circuit-broken position. Fig. 2 is a sectiontaken on the parallel planes A--A of Fig. 1 with parts in same relationas therein shown and with the casing and control button appearing. Fig.3 is a partial plan view, otherwise like Fig. 1 generally but with partsin the circuit-making position. Fig. 4 is a detail perspective view ofthe shaft and certain allied parts. Fig. 5 a partial section taken onthe horizontal plane 13-13 of Fig. 2. the parts being shown in theintermediate position. or the one assumed after the button has beenturned to its circuitbreaking position and while the thermostat isheating. Fig. 6 shows a detail of certain parts taken on the horizontalplane CC of '55 actual cessation of the light, is not only of Fig. 2,said'parts being positioned as in Figs. 1 and 3. Fig. 7 is a viewsimilar to Fig. 3 but showing the intermediate position of parts abovereferred to. Fig. 8 shows the parts of Fig. 6 positioned correspondinglyto Fig. 7 Fig. 9 is a detail view taken in section on the plane DD inFig. 8. Fig. 10 is a diagram of electrical connections of thesingle-pole type of switch illustrated in the above figures; and Fig. 11is a diagram of electrical connections suitable for a double-pole typeof otherwise similar switch wherein the heat generating resistance unitis shown connected in shunt to the switch governed load when the controlbutton is turned for causing delayed opening of the main contacts.

Throughout the several views of the drawings, identical parts aredesignated by the same reference numerals.

In the drawings, Fig. 1 to 9 inclusive, the button is shown at 1 and theshaft at 2, the latter being guided in bearings 3, at, mounted upon theporcelain base 5. The shaft also carries, fixed to it, a collar 6 havinga notch 7 engaged by one end of a coiled spring 8 the other end of whichis attached to a portion 30 of a plate 11 hereinafter described. Thisshaft also carries a cam 9 adapted to engage a radially sliding dog 10guided in a recess plate 11 attached to and insulated from contact clips12, 12. These clips are adapted to engage blades 13, H, mounted upon thebase 5. At the lower end of the shaft 2, below the base 5, is attached aplate 15 arranged to engage, successively, and at diametrically oppositepoints, a spring pawl 16 mounted upon the base 5. This plate 15 carries,insulated from it, contact clips 17, 17, adapted to engage blades 18,19, mounted upon the base 5.

A bi-metallic thermostat. arranged with the more expansible metalinside, is shown -at 20, and is mounted upon the base 5 by means of thebracket 21. This thermostat carries, at its opposite end from saidbracket, a small plate 22 provided with a screw stud 23 engaging one endof a bell crankv 2 5 through a slot therein. This latter lever ispivoted at 26 to the bracket 21.

and has, at its other end, a stud 27 fitted with H a loose roller 28adapted to engage, successively, the opposite extensions 29, 29, of the.recess plate 11. The thermostat is covered, with some suitable materialsuch as asbestosv or mica, and is provided with a heating reslstancewinding 33.

. l A ratchet 36 is fixed to the bracket 21 and arranged to engage aprojection 34 of the sliding dog 10, as later set forth.

Operation is as follows, starting from the circuit-broken position ofthe switch as shown in Fig. 1,the button 1 is turned right handed in theusual manner, which rotatesthe shaft 2 and therewith the cam 9,

the latter causing the dog 10 to slide radially and outwardly until itsprojection 34 disengages the tooth 35 of the fixed ratchet 36.

At the same time the coil spring 8 is placed under tension and therebysnaps the clips 12, 12, into engagement with their blades 13, 14:, thusclosing the main circuit. Just pre vious to this, however, the clips 1717, have been moved into engagement with their blades 18, 19, thusshunting out the resistance 33.

While these operations have been taking The switch is now closed andoperates as a' simple single pole switch.

Referring to the diagram of connections in Fig. 10, it is seen thatcurrent passes from line 37 through main contacts, here indicated at 38,then by way of wire 39 and auxiliary contacts, indicated at 10, aroundthe resistance 33 and so to the load line 11, the resistance 33 beingtherefore practically dead.

When it is desired to open the switch, the button is rotated in the samedirection until caught and held by the engagement of the plate 15 withthe spring pawl 16. The main contacts are held closed by the engagementof the roller 28 with the projection 29 of the plate 11. Thus the coiledspring 8 is held under operative tension, ready to act to break the maincontacts when the same are freed. At the same time the rotation of theshaft has opened the auxiliary contacts 1718, 1719, thus causing theentire line current to flow through the winding 33, which heats,bendsthe thermostat, and frees the roller 28 from the pro'ection 29, as shownin broken lines'in Fig. The stored energy of the coiled spring now snapsopen the main contacts, thus breaking the circuit, both through load andresistance.

The intermediate relation of pa.rts,i. e..

therelation after the button has been turned to its circuit breakingposition but before the main contacts are released to open,is'

shown in Fig. 7 and the relation after the said main contacts are openedof course appears in Fig. 1, save that in said figure the thermostat isshown as cooled.

The time element which shall elapse between the turning ofl of thebutton and the j rupture of the main circuit may readily be varied, witha given load, by altering the size or number of turns of the resistance33,the size of the thermostat,-the engage- .with the resistance in shuntto the load volt age, the said switch being here preferably of thedouble pole'type, or, at least, of a type carrying both poles of thecircuit as required for a shunt connection. I have not thought itneedful to specifically illustrate this type as it merely involves theaddition of a pair of contacts and a re-arrangement of the relativeposition of main and auXil-' be noted that the shunt circuit containingresistance 33 is tapped from the load side of the main contacts so thatupon opening of the latter, said resistance is denergized.

It is evident that when the button 1 is rotated to the OH position, andwhile the thermostat is heating to free the switch contacts to separate,the controlling parts including said button are operatively lockedagainst further movement. That is, the operator having once turned thebutton to the off position cannot turn same further, or to the onposition, again until the switch contacts have opened. In this mannermistakes on the part of users of the switch are prevented, particularlyin the case where no visible change is brought about by the movement onthe button to the off position,- as when no indicator plate is used.

I find that the use of an indicator plate 32, placed above the collar 6in the usual manner, is of advantage as showing the opment in otherforms and arrangements of switch mechanisms than the specific exampleherein disclosed for illustrative purposes only. Without thereforelimiting myself to the precise embodiments of my invention herein shown,what I claim is 1. In a two-branch -circuit controlling switch, incombination; master contacts arranged in series with thetwo-branch-circuit, a detent positioned normally to malntain said mastercontacts closed, thermo-dynamic means operatively related to said detentupon thermal energization to release said master contacts therefrom, aheating device.

in one branch of said two-branch-circuit for said thermo-dynamic means,control means adapted to put said .master contacts under tension forautomatic opening, auxiliary contacts in the other branch of saidtwo-branchcircuit, and manually controllable means for opening saidauxiliary contacts simultaneously with the tensioning of said mastercontacts, whereby said heating device may be rendered operativethermally toenergize the said thermo-dynamic device.

In a two-branchcircuit controlling switch, in combination; mastercontacts arranged in series with the twd-branch-circuit, a detentpositioned normally to maintain said master contacts closed,thermo-dynamic means operatively related to said detent upon thermalenergization to release said master contacts therefrom, a heating devicein one branch of said tWo-branch-circuit for said thermo-dynamic means,auxiliary contacts in the other branch of said two-branchcircuit,manually controllable means for establishing tension tending to opensaid master contacts and also for operating said auxiliary contacts,whereby said heating device may be rendered operative thermallytoenergize the said thermo-dynamic device.

3. In a two branch circuit controlling switch, in combination; mastercontacts arranged in series with the two-branch-circuit, a detentpositioned normally to maintain said master contacts closed,thermo-dynamic means operatively related to said detent upon thermalenergization to release said master contacts therefrom, a heating devicein one branch of said two-b-ranch-circuit for said thermo-dynamic means,auxiliary contacts in the other branch of said two-branchcircuit, andmenu ally-actuated control means arranged upon one actuation to closeboth said master contacts and said auxiliary contacts, and furtherarranged upon subsequent actuation to open said auxiliary contacts andto tension said master contacts for the automatic opening thereof. a. Aone-way, rotary snap switch embodying in combination; stationary contactmembers, a rotary contact device adapted conductively to bridge saidmembers, manually operable means for controlling said device, aresilient connection between said device and said means, detentmechanism arranged cooperatively with said' resilient connection toproduce a quick, tension-caused, followup movement of saiddevicerelative to'said means, a detent and controlling thermostattherefor positioned normally to retain said device in itscontact-bridging position, a

latch arranged automatically to hold said means rotatively advanced andseparated from said device against the tension in said resilientconnection, and a heating circuit for said thermostat, with connectionsoperative to energize said circuit when said means are so heldrotatively seperated from said device.

5. A one-Way, rotary snap switch embodying in combination; stationarycontact members, a rotary contact device adapted conductively to bridgesaid members, manually operable means for controlling said device, aresilient connection between said device and said means, detentmechanism arranged cooperatively with said resilient connection toproduce a quick, tension-caused, follow-up movement of said devicerelative to said means, a detent and controlling thermostat thereforpositioned normally to retain said device in its contact-bridgingposition, a latch arranged automatically to hold said means rotativelyadvanced and separated from said device against the tension in saidresilient connection, and a heating circuit for said thermostat, withconnections operatively to energize said circuit when said means are soheld rotatively separated from said device, said connections beingfurther arranged so that said circuit is automatically denergized bycontact opening movement of said device.

6; A one-way, rotary snap switch embodying in combination; stationarycontact members, a rotary contact device adapted conductively to bridgesaid members, manually operable means for controlling said device, aresilient connection between said device and said means, detentmechanism arranged cooperatively with said resilient connection toproduce a quick, tension-caused, follow-up movement of said devicerelative to said means, a detent and controlling thermostat thereforpositioned normally to retain said device in its contact-bridgingposition, a latch arranged automatically to hold said means rotativelyadvanced and separated from said device against the tension in saidresilient connection, and a heating circuit for said thermostat, withconnec tions automatically to establish said circuit solely in serieswith the switch governed load when said means are so held rotatively searated from said device.

In an electric switch, in combination; manually controllable device forestablishing the main switch contacts in normal closed relation and nottensioned for opensaid contacts for opening movement, an.

electrical resistance arranged in heating relation to the thermostat,and circuit connections governed by said device whereby contact-closingmovement of said device establishes a two-path series-parallelconnection through the switch, one path thereof containing saidresistance and the other path thereof forming a shunt circuit aroundsaid resistance; together with means arranged automatically to open saidshunt circuit simultaneously with the tensioning of said contacts.

8. A snap switch embodying in combination; a rotary contact de ice,manually con-- trollable means for rotating said device, an auxiliarycontact device operably related to said means, a resilient connectionbetween said means and said rotary device, detent mechanism adaptedautomatically to cause a quick, follow-up movement of said rotary devicerelative to said means, a latch arranged to arrest said means in aposition tensioning said rotary device for circuit breaking movement, adetent and controlling thermostat therefor positioned normally toprevent circuit breaking movement of said rotary device, and a. heatingcircuit for the thermostat, adapted to be energized by movement of saidmeans to its said tensioning position.

9. In a one-way snap switch, in combination with a circuit-gove1'ning,spring-actuated rotary contact device, and a thermostat arrangedautomatically to control the movement thereof, a radially projectingmember carried by the said device and a pivoted detent lever having oneend thereof adapted to engage with said projection for preventingmovement of said device, and having the said thermostat operativelyconnected to another portion thereof, the said detent lever beingpivoted substantially upon a line tangential to the arc of movement ofsaid projecting member.

10. In an electric circuit switch, manually controlledmeans adapted atone actuation thereof to close the switch and at the next actuationthereof to energize mechanism tending to open the switch, means toretain the said switch closed, means to lock the said controlling meansagainst reverse movement aftersaid second actuation thereof; togetherwith a thermostat to govern the said retaining means, and a heatingcircuit for the said thermostat, the said heating circuit beingenergized by the said second actuation of the manual controlling means.

11. In a thermostatically governed electric switch, in combination withthe contact members having relative movement to open and to close theswitch, and a thermostatic detent to restrain said opening movement,controlling means to close the switch and to IIO cause opening of theswitch, and means to lock said controlling means in inoperative relationto the switch contacts after said means have been moved to a positionadapted to cause opening of the switch and until said switch is opened.

12. In a single pole electric switch, in combination; master contactmembers and a detent normally positioned coiiperatively therewith toprevent circuit breaking move ment of said members, a thermo-dynamicdevice arranged coiiperatively with resilient means whenenergizedautomatically to open said contacts; a two-path, dividedcircuit in series with said master contacts including in one branchthereof said device, auxiliary contacts arranged in the other branch ofsaid divided circuit, and common manual controlling means for both saidmaster and said auxiliary contacts.

13. In a single pole, electric switch, in combination; movable contactmembers and a detent normally positioned cooperatively therewith toprevent circuit breaking movement of said members, a thermo-dynamic device arranged cooperatively with resilient means when energizedautomatically to separate said members, a circuit governed by saidcontact members, including in one'branch thereof said device, auxiliarycontacts for short-circuiting said device, and manual controlling mea-nsarranged to close both said members and said auxiliary contacts, andupon subsequent actuation thereof to establish tension tending toseparate said members and simultaneously to open said auxiliarycontacts.

14. In a single pole, electric switch, in combination; master contactmembers and a detent normally positioned cooperatively therewith toprevent circuit breaking movement of said members, a thermodynamicdevice arranged cotiperatively with resilient means when energizedautomatically to open said contacts; a two-path divided circuit inseries with said master contacts including in one branch thereof saiddevice, auxiliary contacts arranged in the other branch of said dividedcircuit, and manual controlling means arranged simultaneously to closeboth said master and said auxiliary contacts and upon subsequentactuation thereof to open said auxiliary contacts and simultaneously toestablish tension tending to open said master contacts 15. In a rotarysnap switch including an insulating base, stationary contact terminalsmounted thereon and a rotatable contact device carrying a contact plateinsulated therefrom and adapted in alternate sta es of rotativeprogression conductively to ridge said terminals, in combination; aconcentrically pivoted shaft having resilient and detent connection withsaid device for ing position, a spring detent mounted beneath theinsulating base and adapted to hold said shaft relatively advanced andseparated under tension from said device when the latter is sointercepted, a thermostat and heating circuit therefor arranged whenenergized to actuate said lever and release said device, and'anauxiliary current switch positioned beneath the insulating base andadapted to be operated by movement of said shaft, whereby said heatingcircuit may be electrically energized when said device is tensioned forcircuit breaking movement.

16. In an electric switch embodying a 1'0- table, contact-bridgingstructure for controlling the main circuit, said structure beingarranged to engage conductively with stationary circuit terminals inalternate stages of progressive rotation, and embodying also anactuating device for said structure, having tensioned connection theretoand stop means positively preventing reverse movement of said structureand of said device between said stages, in combination; a movable detentnormally arranged and positioned to intercept circuit-breaking movementof the said contact-bridging structure; a pawl detent operativelyassociated with the said actuating device thereby to hold the latter inposition tensioning said structure for movement into a circuit breakingposition; a thermostat normally positioned and formed cotiperativelywith said movable detent to prevent the release of said structure fromsaid movable detent; a normally inactive electric heating unit for thethermostat; and auxiliary switch means operably related to the saidactuating device and elec trically connected, when said device occupiesits said tensioning position, to divert current through said electricheating unit, thereby to energize operably the thermostat for causing adelayed release of said structure from said movable detent.

17. In an electric switch embodying a rotatable, contact-bridgingstructure for controlling the main current; said structure be ingarranged to engage conductively with stationary circuit terminals inalternate stages of progressive rotation, and. embodying also anactuating device for said structure having tensioned connection there toand stop means positively preventing reverse movement of said structureand of said device between said stages, in combination; a movable detentnormally arranged and positioned to intercept circuit breaking movementof the said contact-bridging structure; a pawl detent operativelyassociated with the said actuating device thereby to hold the latter inposition tensioning said structure for movement into a circuit breakingposition; a thermostat normally positioned and formed coiiperativelywith said movable detent to prevent the release of said structure fromsaid movable detent,

a normally, inactive electric heating unit for the thermostat; and anauxiliary contact bridging structure fixedly carried by said actuatingdevice, and positioned thereon, when said device occupies its saidtensioning position, to divert current through said electric heatingunit, thereby to energize operably the thermostat for causing a delayedrelease of said structure from said movable detent.

18. In a current supplied electric circuit, the combination of a load, acut-out, and a divided circuit all in series, said divided circuitcontaining in one branch thereof, a current governed device operativelyrelated to said cut-out, and said divided circuit containing in anotherbranch thereof a current switching means for governing the supply ofcurrent to said device.

19. An electric switch embodying a progressively rotatable contactmember; an actuator. element mounted for progressive step-by-steprotative movement relatively in advance of said members; a spring and detent connection between said member and said element whereby rotativeadvances of said element relative to said member cause quick, follow-uprotative movements of said member, respectively to make and to break acircuit; a separate detent arranged to prevent said follow-up movementof said memher from its circuit-making position when said element isrotatively advanced; means to hold said element so rotatively advanced,whereby said member is tensioned for cir- 'cuit-breaking movement; andnormally inactive, slow-acting, instrumentalities arranged to beoperatively energized by the said rotative advance of-said element, andthereby rendered operative to tree sald con-' tact from said separatedetent after a predetermined interval of time.

Signed at Braintree, in the county of Norfolk and Commonwealth ofMassachusetts, this 16th day of September, 1915.

MALCOLM H. BAKER.

Witnesses SELoRI AMoRoso, RAYMOND D. SMITH.

